custom static method

TransitionFunction custom(num amount)

Implementation

static TransitionFunction custom(num amount) {
  if (amount < -1) amount = -1;
  if (amount > 1) amount = 1;

  num easing(num t) {
    if (amount == 0) return t;
    if (amount < 0) return t * (t * -amount + 1 + amount);
    return t * ((2 - t) * amount + (1 - amount));
  }

  return easing;
}